/*
 * Copyright (c) 2000, 2004, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.imageio.spi;

import java.io.File;
import java.io.IOException;
import javax.imageio.stream.ImageInputStream;

/**
 * The service provider interface (SPI) for
 * <code>ImageInputStream</code>s.  For more information on service
 * provider interfaces, see the class comment for the
 * <code>IIORegistry</code> class.
 *
 * <p> This interface allows arbitrary objects to be "wrapped" by
 * instances of <code>ImageInputStream</code>.  For example,
 * a particular <code>ImageInputStreamSpi</code> might allow
 * a generic <code>InputStream</code> to be used as an input source;
 * another might take input from a <code>URL</code>.
 *
 * <p> By treating the creation of <code>ImageInputStream</code>s as a
 * pluggable service, it becomes possible to handle future input
 * sources without changing the API.  Also, high-performance
 * implementations of <code>ImageInputStream</code> (for example,
 * native implementations for a particular platform) can be installed
 * and used transparently by applications.
 *
 * @see IIORegistry
 * @see javax.imageio.stream.ImageInputStream
 */
public abstract class ImageInputStreamSpi extends IIOServiceProvider {

  /**
   * A <code>Class</code> object indicating the legal object type
   * for use by the <code>createInputStreamInstance</code> method.
   */
  protected Class<?> inputClass;

  /**
   * Constructs a blank <code>ImageInputStreamSpi</code>.  It is up
   * to the subclass to initialize instance variables and/or
   * override method implementations in order to provide working
   * versions of all methods.
   */
  protected ImageInputStreamSpi() {
  }

  /**
   * Constructs an <code>ImageInputStreamSpi</code> with a given set
   * of values.
   *
   * @param vendorName the vendor name.
   * @param version a version identifier.
   * @param inputClass a <code>Class</code> object indicating the legal object type for use by the
   * <code>createInputStreamInstance</code> method.
   * @throws IllegalArgumentException if <code>vendorName</code> is <code>null</code>.
   * @throws IllegalArgumentException if <code>version</code> is <code>null</code>.
   */
  public ImageInputStreamSpi(String vendorName,
      String version,
      Class<?> inputClass) {
    super(vendorName, version);
    this.inputClass = inputClass;
  }

  /**
   * Returns a <code>Class</code> object representing the class or
   * interface type that must be implemented by an input source in
   * order to be "wrapped" in an <code>ImageInputStream</code> via
   * the <code>createInputStreamInstance</code> method.
   *
   * <p> Typical return values might include
   * <code>InputStream.class</code> or <code>URL.class</code>, but
   * any class may be used.
   *
   * @return a <code>Class</code> variable.
   * @see #createInputStreamInstance(Object, boolean, File)
   */
  public Class<?> getInputClass() {
    return inputClass;
  }

  /**
   * Returns <code>true</code> if the <code>ImageInputStream</code>
   * implementation associated with this service provider can
   * optionally make use of a cache file for improved performance
   * and/or memory footrprint.  If <code>false</code>, the value of
   * the <code>useCache</code> argument to
   * <code>createInputStreamInstance</code> will be ignored.
   *
   * <p> The default implementation returns <code>false</code>.
   *
   * @return <code>true</code> if a cache file can be used by the input streams created by this
   * service provider.
   */
  public boolean canUseCacheFile() {
    return false;
  }

  /**
   * Returns <code>true</code> if the <code>ImageInputStream</code>
   * implementation associated with this service provider requires
   * the use of a cache <code>File</code>.  If <code>true</code>,
   * the value of the <code>useCache</code> argument to
   * <code>createInputStreamInstance</code> will be ignored.
   *
   * <p> The default implementation returns <code>false</code>.
   *
   * @return <code>true</code> if a cache file is needed by the input streams created by this
   * service provider.
   */
  public boolean needsCacheFile() {
    return false;
  }

  /**
   * Returns an instance of the <code>ImageInputStream</code>
   * implementation associated with this service provider.  If the
   * use of a cache file is optional, the <code>useCache</code>
   * parameter will be consulted.  Where a cache is required, or
   * not applicable, the value of <code>useCache</code> will be ignored.
   *
   * @param input an object of the class type returned by <code>getInputClass</code>.
   * @param useCache a <code>boolean</code> indicating whether a cache file should be used, in cases
   * where it is optional.
   * @param cacheDir a <code>File</code> indicating where the cache file should be created, or
   * <code>null</code> to use the system directory.
   * @return an <code>ImageInputStream</code> instance.
   * @throws IllegalArgumentException if <code>input</code> is not an instance of the correct class
   * or is <code>null</code>.
   * @throws IllegalArgumentException if a cache file is needed but <code>cacheDir</code> is
   * non-<code>null</code> and is not a directory.
   * @throws IOException if a cache file is needed but cannot be created.
   * @see #getInputClass
   * @see #canUseCacheFile
   * @see #needsCacheFile
   */
  public abstract ImageInputStream
  createInputStreamInstance(Object input,
      boolean useCache,
      File cacheDir) throws IOException;

  /**
   * Returns an instance of the <code>ImageInputStream</code>
   * implementation associated with this service provider.  A cache
   * file will be created in the system-dependent default
   * temporary-file directory, if needed.
   *
   * @param input an object of the class type returned by <code>getInputClass</code>.
   * @return an <code>ImageInputStream</code> instance.
   * @throws IllegalArgumentException if <code>input</code> is not an instance of the correct class
   * or is <code>null</code>.
   * @throws IOException if a cache file is needed but cannot be created.
   * @see #getInputClass()
   */
  public ImageInputStream createInputStreamInstance(Object input)
      throws IOException {
    return createInputStreamInstance(input, true, null);
  }
}
